Aims. NSV 13983 is catalogued as a dwarf nova based on a reported outburst
from 2005. The system has not yet been studied spectroscopically. We attempt to
confirm its nature as a dwarf nova and determine its orbital period.
Methods. We derive the orbital period by using time-resolved spectroscopic
data to measure radial velocities.
Results. The average spectrum shows evidence that the system is a dwarf nova
in quiescence. The radial velocity curves derived from measurements of the
spectral lines H\alpha and H\beta, show a clear modulation with a period of
2.76 h. This places NSV 13983 below the upper edge of the gap in the period
distribution of cataclysmic variables, implying that it is the 14th dwarf nova
in the gap.Comment: 3 pages, 4 figures, 1 tables, accepted by A&
